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Mold in Your HVAC System: What You Need to Know

Typically when we think of mold, we think of it growing on the walls, in a flooded basement or in the bathroom. These are common areas, but mold can also grow in your HVAC system. When that happens, it can hurt the operation of your HVAC system as well as filter mold into the air to spread throughout the house. It also negatively impacts your indoor air quality. Respiratory problems and in the worst case nausea and vomiting are common symptoms of exposure to mold.

Fortunately, there are actions you can take when you have mold in your HVAC system. First, it’s important to know what can cause mold to grow in your HVAC system.


The most common cause of mold in your HVAC system is moisture, especially during the summer when you need air conditioning. When your system collects hot air from outside in order to condition it, it also collects the humidity from outside. Additionally, many AC units condition the air by liquefying it. This creates moist, humid conditions that are the perfect breeding grounds for various species of mold.

If you already have mold in your home, mold spores released into the air may also gather on the air filter, which can cause it to grow there. Mold spores may also be circulated back into the home, which can cause a previously existing mold problem to grow.


It might not be immediately obvious that you have mold growing in your HVAC system, so there are a few signs to watch out for. The first is actually seeing mold in or around ducts or vents. However, you might also smell a musty, earthy smell indicative of mold. You should also watch your own health and that of your family. Mold exposure symptoms are similar to allergy/sinus symptoms: coughing, sneezing, sinus congestion and difficulty breathing. You may develop rashes, and in extreme cases, you may experience headaches, nausea, or vomiting.

What to Do

If you have mold in your HVAC system, the first thing to do is to turn it off completely. If you haven’t already called an HVAC inspector, do so. Do not try to clean the system yourself — this is a job for professionals. They’ll remove air filters and wet insulation and then vacuum out any standing water. Next, they’ll use disinfectant specifically designed to kill mold. Finally, they should apply a mold and mildew inhibitor to each part of the HVAC system, thus preventing the problem in the future.

Mold in your HVAC system is nothing to be taken lightly, but it’s also something that can be fixed. At Air Solutions in Bryan-College Station, our 50 years of combined experience more than qualifies us to help clean your HVAC system in the event of mold. We can even make suggestions to help you avoid the problem altogether. Contact us today for more information.

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